Comparison of Passive and Semi-Active Horizontal Platform Suspensions

In this paper modelling, control and optimization of a kinematically excited horizontal platform is presented. The platform with two independent mutually perpendicular suspension units is designed to mitigate horizontal vibration of the operator seat in the excavator cabin. Three types of suspension between the lower part of the platform and the cabin and between the lower part and the upper part of the platform are investigated, namely passive suspension, idealized semi-active suspension and suspension equipped with magnetorheological dampers. Their design parameters are optimized. The improvement of the magnetorheological/idealized semi-active platform suspension in reducing the vibration total value of the frequency weighted effective accelerations in two mutually perpendicular horizontal directions, compared with the passive platform suspension, is 26,3%/70,8%. The magnitude of the vibration total value of the passive/magnetorheological/idealized semi-active platform suspension is 0,4547m·s−2 (a little uncomfortable)/0,3352 m·s−2 (a little uncomfortable)/0,1328 m·s−2 (not uncomfortable)

Understanding Calculus Through Maple-Based Dynamic Visualization Tools

First-year college students experience difficulties in understanding the concepts of derivatives and integrals. At the postsecondary level, the use of static visualization and other traditional instruction delivery methods often are unable to meet students\u27 needs in calculus. This problem is current and essential in the field of education and needs consideration to enhance the method of teaching calculus. The rationale for this study was to scrutinize the effects of Maple dynamic visualization instructional activities, within the framework of the animation-visualization theory, on students\u27 conceptual and procedural understanding of differential and integral calculus. The usage of a quantitative 2x2 factorial pretest-posttest control group quasi-experimental mixed design, with multivariate analysis of variance for data (de-identified list of 81 students\u27 test scores on derivatives and integrals) analyses, helped examine the relationships between the research variables. Results showed that the Maple dynamic visualization group, significantly (p \u3c 0.001), outperformed the non-Maple static visualization group with a significant interaction between the groups with a substantial effect size of at least 0.27. This study augments the body of evidence that supported the efficacy of animated visuals over static visuals in producing more exceptional academic performance. A future researcher should use the random assignment to groups to minimize the possibilities of nonequivalent groups and the same measure for pretest and posttest. This study provides a groundwork for positive social change to reach a shared vision in education, enable learners to gain skills in calculus, and prepare students in and for science, technology, engineering, and mathematics majors and careers

Analysis the brachistochronic motion of a mechanical system with nonlinear nonholonomic constraint

U ovom radu analizira se problem brahistohronog ravnog kretanja mehaničkog sistema sa nelinearnom neholonomnom vezom. Neholonomni mehanički sistem je predstavljen sa dva Čapljiginova sečiva, zanemarljivih dimenzija, koja nameću nelinearno ograničenje u vidu upravnosti brzina. Razmatra se brahisthrono ravno kretanje pri zadatom početnom i krajnjem položaju uz neizmenjenu vrednost mehaničke energije u toku kretanja. Diferencijalne jednačine kretanja, u kojima figurišu reakcije neholonomnih veza i upravljačkih sila, dobijene su na osnovu opštih teorema dinamike. Ovde je to podesnije umesto nekih drugih metoda analitičke mehanike primenjenih na neholonomne mehaničke sisteme u kojima je neophodno dati naknadno fizičko tumačenje množitelja veza. Formulisan brahistohroni problem, uz odgovarajući izbor veličina stanja je rešen kao, najjednostavniji u ovom slučaju, zadatak optimalnog upravljanja primenom Pontryagin-ovog principa maksimuma. Dobijen je odgovarajući dvotačkasti granični problem sistema običnih nelinearnih diferencijalnih jednačina koji je neophodno numerički rešiti. Numerički postupak za rešavanje dvotačkastog graničnog problema vrši se metodom šutinga. Na osnovu tako dobijenog brahistohronog kretanja određuju se aktivne upravljačke sile, a ujedno i reakcije neholonomnih veza. Koristeći Kulonove zakone trenja klizanja, određuje se minimalno potrebna vrednost koeficijenta trenja klizanja, tako da se razmatrani sistem kreće u skladu sa neholonomnim zadržavajućim vezama.This paper analyzes the problem of brachistochronic planar motion of a mechanical system with nonlinear nonholonomic constraint. The nonholonomic system is represented by two Chaplygin blades of negligible dimensions, which impose nonlinear constraint in the form of perpendicularity of velocities. The brachistrochronic planar motion is considered, with specified initial and terminal positions, at unchanged value of mechanical energy during motion. Differential equations of motion, where the reactions of nonholonomic constraints and control forces figure, are obtained on the basis of general theorems of mechanics. Here, this is more convenient to use than some other methods of analytical mechanics applied to nonholonomic mechanical systems, where a subsequent physical interpretation of the multipliers of constraints is required. The formulated brachistochrone problem, with adequately chosen quantities of state, is solved as simple a task of optimal control as possible in this case by applying the Pontryagin maximum principle. The corresponding two-point boundary value problem of the system of ordinary nonlinear differential equations is obtained, which has to be numerically solved. Numerical procedure for solving the two-point boundary value problem is performed by the method of shooting. On the basis of thus obtained brachistochronic motion, the active control forces, along with the reactions of nonholonomic constraints, are defined. Using the Coulomb friction laws, a minimum required value of the coefficient of sliding friction is defined, so that the considered system is moving in accordance with nonholonomic bilateral constraints

Elements of dynamic parameters modification and sensitivity

Promene na konstrukcijama mogu izazvati promene u strukturnim matricama nekih elemenata. U zavisnosti od vrste konstrukcije, kao i od željenih promena u njoj, moguće je menjati veću ili manju grupu elemenata. U ovom radu se analiziraju efekti malih i velikih modifikacija grupa elemenata na sopstvene vrednosti i frekvencije. Analiza se vrši korišćenjem kompjuterskih programa zasnovanim na metodi konačnih elemenata i implementaciji distribucije potencijalne i kinetičke energije na glavnim oblicima oscilovanja u posmatranim elementima konstrukcije.Structural modifications can cause changes in the matrices of some elements. Depending on the type of structure, or a desired change, a group of elements can be modified. This paper analyzes the effects of small and large-scale modifications of some groups of elements on structural eigenvalues and frequencies. The process of analysis is done using a computer program, based on using of finite element methods and the implementation of structure energy distributions

Analysis the brachistochronic motion of a mechanical system with nonlinear nonholonomic constraint

U ovom radu analizira se problem brahistohronog ravnog kretanja mehaničkog sistema sa nelinearnom neholonomnom vezom. Neholonomni mehanički sistem je predstavljen sa dva Čapljiginova sečiva, zanemarljivih dimenzija, koja nameću nelinearno ograničenje u vidu upravnosti brzina. Razmatra se brahisthrono ravno kretanje pri zadatom početnom i krajnjem položaju uz neizmenjenu vrednost mehaničke energije u toku kretanja. Diferencijalne jednačine kretanja, u kojima figurišu reakcije neholonomnih veza i upravljačkih sila, dobijene su na osnovu opštih teorema dinamike. Ovde je to podesnije umesto nekih drugih metoda analitičke mehanike primenjenih na neholonomne mehaničke sisteme u kojima je neophodno dati naknadno fizičko tumačenje množitelja veza. Formulisan brahistohroni problem, uz odgovarajući izbor veličina stanja je rešen kao, najjednostavniji u ovom slučaju, zadatak optimalnog upravljanja primenom Pontryagin-ovog principa maksimuma. Dobijen je odgovarajući dvotačkasti granični problem sistema običnih nelinearnih diferencijalnih jednačina koji je neophodno numerički rešiti. Numerički postupak za rešavanje dvotačkastog graničnog problema vrši se metodom šutinga. Na osnovu tako dobijenog brahistohronog kretanja određuju se aktivne upravljačke sile, a ujedno i reakcije neholonomnih veza. Koristeći Kulonove zakone trenja klizanja, određuje se minimalno potrebna vrednost koeficijenta trenja klizanja, tako da se razmatrani sistem kreće u skladu sa neholonomnim zadržavajućim vezama.This paper analyzes the problem of brachistochronic planar motion of a mechanical system with nonlinear nonholonomic constraint. The nonholonomic system is represented by two Chaplygin blades of negligible dimensions, which impose nonlinear constraint in the form of perpendicularity of velocities. The brachistrochronic planar motion is considered, with specified initial and terminal positions, at unchanged value of mechanical energy during motion. Differential equations of motion, where the reactions of nonholonomic constraints and control forces figure, are obtained on the basis of general theorems of mechanics. Here, this is more convenient to use than some other methods of analytical mechanics applied to nonholonomic mechanical systems, where a subsequent physical interpretation of the multipliers of constraints is required. The formulated brachistochrone problem, with adequately chosen quantities of state, is solved as simple a task of optimal control as possible in this case by applying the Pontryagin maximum principle. The corresponding two-point boundary value problem of the system of ordinary nonlinear differential equations is obtained, which has to be numerically solved. Numerical procedure for solving the two-point boundary value problem is performed by the method of shooting. On the basis of thus obtained brachistochronic motion, the active control forces, along with the reactions of nonholonomic constraints, are defined. Using the Coulomb friction laws, a minimum required value of the coefficient of sliding friction is defined, so that the considered system is moving in accordance with nonholonomic bilateral constraints

Variation de la densité et la couleur du bois de Pterocarpus erinaceus (Poir) en fonction des conditions environnementales en Afrique de l’Ouest

National audiencePterocarpus erinaceus (Poir.) is currently spontaneous species of Guinea-Sudanese and Sudano-Sahelian areas overexploited and threatened in West Africa. This paper analyzes the density and color of the wood of the species in the agro-ecological zones of three countries in West Africa (Togo, Burkina Faso and Niger). The results of 452 samples collected from 95 trees from the three countries show significant differences in values of basic density and color parameters (P <0.05) according to agro-ecological zones (Sudan, Guinea and Sahel). At scale intra-tree, even if there is an increase in density with the number of rings counted from the pith, this increase is very small (R²≤ 0.18). This reflects the fact that age has little influence on the trees density. In addition, a significant correlation was observed between density and color parameters.Pterocarpus erinaceus (Poir.) est actuellement l’espèce spontanée des zones guinéo-soudaniennes et soudano-sahéliennes très exploitée et menacée en Afrique de l’Ouest. Le présent travail analyse la densité et la couleur du bois de l’espèce dans les zones agroécologiques de trois pays de l’Afrique de l’Ouest (Togo, Burkina Faso et Niger). Les résultats obtenus sur 452 éprouvettes prélevées de 95 arbres issus des 3 pays indiquent des différences significatives des valeurs de l’infradensité et des paramètres de couleur (P<0,05) en fonction des zones agro-écologiques (soudanienne, guinéenne et sahélienne). A l’échelle intra-arbre, même s’il ya une augmentation de la densité en fonction du nombre de cernes comptés, depuis la moelle, cette augmentation est très faible (R²≤ 0,18). Ce qui traduit le fait que l’âge des arbres influence peu l’infradensité. Par ailleurs une corrélation significative a été observée entre la densité et les paramètres de couleur

A Google-inspired error-correcting graph matching algorithm

Graphs and graph algorithms are applied in many different areas including civil engineering, telecommunications, bio-informatics and software engineering. While exact graph matching is grounded on a consolidated theory and has well known results, approximate graph matching is still an open research subject. This paper presents an error tolerant approximated graph matching algorithm based on tabu search using the Google-like PageRank algorithm. We report preliminary results obtained on 2 graph data benchmarks. The first one is the TC-15 database [14], a graph data base at the University of Naples, Italy. These graphs are limited to exact matching. The second one is a novel data set of large graphs generated by randomly mutating TC-15 graphs in order to evaluate the performance of our algorithm. Such a mutation approach allows us to gain insight not only about time but also about matching accuracy

Évaluation de la productivité technique de trois matériels d’étuvage de riz paddy au Bénin

Objectif : L’objectif du travail est d’évaluer la productivité technique de trois équipements d’étuvage de riz paddy, notamment :-i- le petit kit (marmite+bac) d’une capacité d’étuvage de 80 kg par traitement, -ii- le tonneau basculant d’une capacité de 80 kg et -iii- le grand kit d’une capacité de 300 kg.Méthodologie et résultats : La productivité technique de chacun de ces trois équipements en usage au Bénin a été évaluée par rapport à : la main d’oeuvre/travail (kg de paddy traité /Homme/heure), l’utilisation de bois (kg de paddy traité/kg de bois), l’eau (kg paddy traité/Litre d’eau) et l’investissement (kg de paddy étuvé /100 FCFA investis). Par la suite, les attributs de qualité physique du riz tels que le coeur blanc, l’homogénéité, la dureté et la couleur ont été évalués sur les échantillons du riz étuvé avec chaque matériel d’étuvage. Les résultats obtenus indiquent que le grand kit de 300 kg présente une productivité de travail plus faible (8,98 kg) que les deux autres matériels d’étuvage. Le kit bac+marmite et le matériel d'étuvage tonneau présentent des productivités similaires par rapport à la main-d'oeuvre, l’utilisation de bois, l’eau et le capital investi. Aucune différence significative n’est observée pour la consommation en eau pour les trois matériels testés. A l’exception de la couleur, la qualité physique du riz étuvé avec les trois matériels ne montre aucune différence significative pour le coeur blanc, l’homogénéité et la dureté des grains de riz.Conclusion et application des résultats : Vu la qualité de riz étuvé obtenu après utilisation de ces matériels, le kit bac+marmite ou le kit de grande capacité de 300 kg peuvent être recommandés aux femmes étuveuses en fonction de leur niveau de production. Toutefois des travaux d’améliorations sont nécessaires aussi bien sur le grand kit de 300kg que sur celui en tonneau afin de faciliter leur utilisation et de permettre aux transformatrices de produire de riz étuvé de bonne qualité.Mots-clés : productivité, matériel, étuvage de riz, qualité.Assessment of the productivity of three parboiling equipments in BeninABSTRACTObjective: To evaluate the productivity of three parboiling equipments namely: small kit (Pot + vat with parboiling capacity of 80 kg); barrel of with a capacity of 80 kg and the big kit (tank + vat with a capacity of 300 kg).Methodology and results: The productivity of these three equipments was evaluated with respect to: labor (kg of paddy processed/person/ hour), fire wood (kg paddy processed/kg), water (kg paddy/kg/liter), investment (kg paddy/100FCFA). Thereafter, the physical quality attributes of the parboiled rice such as chalkiness, homogeneity, toughness and the colour of the parboiled rice samples were evaluated. The results indicate that the 300 kg big kit presented low labor productivity of 8.98kg compared to the two other parboiling materials. The small kit (Pot + vat of parboiling capacity 80 kg) and the barrel of a capacity 80 kg present similar productivity in relation to the labor, wood, water and investment. No significant difference is observed for water use during parboiling while using each of the tested materials. Except for the colour, the physical quality of parboiled rice obtained with each of the three materials shows no significant difference for the chalkiness, homogeneity and the toughness of the rice grains.Conclusion and application of results: Concerning the quality of parboiled rice obtained after use of these materials, the small kit or the big kit (tank + vat with a 300 kg capacity) can be recommended to the women parboilers according to their level of production. However, works of improvement are necessary on the big kit of 300kg as well as that of barrel in order to facilitate their use and to allow the processors to produce good quality parboiled rice.Key words: Productivity, equipment, rice, parboiling, quality

Espèces Ligneuses de Savanes Sèches du Nord du Togo : Considérations Socioculturelles et Relations de Pouvoir des Parties Prenantes

Les espèces ligneuses du nord du Togo sont sujettes à de diverses utilisations pour satisfaire des besoins multiples des populations et leur gestion implique plusieurs acteurs. L’objectif de l’étude est d’apprécier les connaissances endogènes de ces espèces ligneuses, les préférences et les similarités. L’approche méthodologique est basée sur des enquêtes ethnobotaniques et socioéconomiques menées auprès de 14 groupes ethniques par interview individuel et par focus groups. Les analyses ont porté sur la Classification Ascendante Hiérarchique (CAH) des usages selon la méthode de Sorensen et sur la catégorisation des parties prenantes. Au sein des différents groupes socioculturels ciblés, il ressort un consensus, notamment sur les espèces utilisées pour une catégorie d’usage donnée. L’utilisation courante des espèces ligneuses est orientée simultanément sur deux grands types d’usages à savoir : (i) usages alimentaires, médicinaux, fourragères et rituels ; et (ii) usages artisanal, bois énergie et bois de service. Elle est rare pour un type spécifique d’usages cosmétiques ou hygiéniques. Ces usages sont similaires à quatre grands regroupements ethniques. Le résultat des inventaires réalisé sur l’ensemble des espèces ligneuses montrent que, 42 de ces espèces présentent une vulnérabilité forte. Les réalités socioculturelles et la promiscuité entre les groupes ethniques déterminent les connaissances et les choix de biens et services écosystémiques. Ainsi, il est recommandé que les programmes d’aménagements forestiers tiennent compte de ces facteurs y compris, les responsabilités locales de même que les influences et les intérêts des parties prenantes. &nbsp; Woody species in northern Togo are used to meet multiple needs of populations and their management involves many actors. The study objective is to appreciate communities’ knowledge of these woody species, preferences, and similarities. The methodology is based on semi-directive ethnobotanical and socioeconomic surveys within 14 ethnic groups through individual interviews and focus groups discussions. The analysis included Hierarchical Upward Classification (HUC) of uses according to the Sorensen method, and on the characterization of the main stakeholders. Within the targeted various socio-cultural groups, there is a consensus, mainly on the species used for a given category of use. It emerges that woody species are frequently used for two goals (food and medicinal; livestock feeding and ritual), or three goals (artisanal, energy wood, and service wood) and rarely for a specific type of use (cosmetic or hygienic). Four main ethnic groups have similarities of uses and 42 out of all of the species identified, present a high vulnerability. Some local socio-cultural realities and promiscuity between ethnic groups determine the knowledge of forest trees and the choices of goods and services. Therefore, it is recommended for forest development programs to take into account the above factors including local responsibilities as well as influences and interests of stakeholders